The present disclosure relates to a DC power relay used for connecting or disconnecting a DC high voltage.
Hybrid vehicles are vehicles in which at least two power sources are used as a driving source. In general, hybrid vehicles are vehicles which utilize an existing internal combustion engine and a motor driven by a battery at the same time. Here, the batteries are recharged using energy generated by the driving of an internal combustion engine or energy lost when being braked. Thus, since the recharged batteries are used for driving vehicles, hybrid vehicles have high-efficiency characteristics when compared to those of existing vehicles which use an internal combustion engine alone.
Such a hybrid vehicle uses an existing engine and a battery as a power source. Particularly, when the hybrid vehicle is initially driven, the hybrid vehicle is accelerated by electricity energy using the battery power source. Then, the battery is repeatedly charged/discharged using the engine and brake according to a running speed. To improve performance of the hybrid vehicle, batteries having higher capacity are required. For this, easiest is to increase a voltage.
Thus, an available voltage of an existing battery, i.e., about 12 V is boosted to about 200 V to about 400V. There is high probability of an additional increase of the battery voltage from now on. As the available voltage of the battery is increased, high insulation performance is required. For this, high-voltage relays for stably turning on/off a power source of a high-voltage battery are being applied to hybrid vehicles.
Such a high-voltage DC relay may break DC current of a high-voltage battery when a contingency arises or according to a control signal of a vehicle controller. Here, an arc may occur when the DC current is connected or disconnected. The arc may have a bad influence on other adjacent instruments or reduce insulation performance. Thus, to adequately control this, a permanent magnet is used. When the permanent magnet is disposed adjacent to a contact of the high-voltage DC relay which generates an arc, the arc may be controlled using a force decided according to intensity and direction of a magnetic flux occurring by the permanent magnet, a current flow direction, and an extension length of the arc. As a result, the arc may be cooled and dissipated. Thus, the DC power relay using the permanent magnet is being applied to electric vehicles such as present hybrid vehicles.
FIG. 1 is a schematic perspective view illustrating an example of a DC power current. Referring to FIG. 1, the DC power relay includes first and second fixed contacts 10 and 11 disposed parallel to each other and a movable contact 12 vertically movably disposed under the fixed contacts 10 and 11. When the movable contact 12 is moved upward to contact the fixed contacts 10 and 11, the DC power relay is turned on. On the other hand, when the movable contact 12 is moved downward and then separated from the fixed contacts 10 and 11, the DC power relay is turned off.
Even as the movable contact 12 is moved downward and thus separated from the fixed contacts 10 and 11, an arc may be generated between the fixed contacts 10 and 11 and the movable contact 12.
Here, if a separate control is not performed, the generated arc may be generated along a straight line between the fixed contacts 10 and 11 and the movable contact 12. As a result, the insulation performance may be reduced, and also, life cycles of adjacent components may be reduced.
To prevent this, first and second permanent magnets 14 and 15 are disposed adjacent to the fixed contact 10 and 11. The permanent magnets 14 and 15 are disposed in a direction perpendicular to that of current flowing through arc plasma to apply a magnetic driving force to the generated arc plasma.
The applied magnetic driving force may separate the arc from the contacts to move the arc in arrow directions, i.e., to the outside. Thus, a distance between the arcs may be increased, and also a length of the arc itself may be extended.
The arc having the extended length may be cooled by gas (air), and thus be changed from a plasma state into an insulated state. This may brake current as well as minimize insulation breaking possibility due to the contact between the arcs.
However, when the movable contact 12 contacts the fixed contacts 10 and 12, and thus the DC power relay is turned on, a downward magnetic driving force is applied to the movable contact 12 on the basis of the Fleming's left-hand law.
Thus, while the DC power relay is turned on, the movable contact 12 may be undesirably separated from the fixed contacts 10 and 11.